The Trespassers, Book 4 - Ferenusia

Spin-off & sequel set in the same world as The Trespassers trilogy.

Magic has almost disappeared. Deprived of it, the Trespassers’ empire is falling to pieces. Sole survivors of this debacle, the Ferrous, faeries reduced to slavery by the Trespassers, have escaped their prisons. With the support of Ferenusia, a clandestine network, their objective is now to obtain the same rights have humans, in a world that knows nothing of their existence. However, their former masters will stop at nothing to keep their secrets, including getting rid of any witness to their crimes. 

All these disruptions are not without consequences for Peter. Particularly when he learns of the accident that took place in the underground tunnels of Maupertius, where Arnaut decided to stay behind…